MTFCA Forum

Hi all,
The radiator drain petcock threads/radiator threads are worn and the petcock doesn't lock in. What can I do to fix this? solder the petcock in? wrap the petcock with teflon tape (what I have now)? What would give me a good hold. The teflon tape is working, but the petcock has a little movement. Thanks all,
John

Drill a new hole about an inch away from the old hole and tap it with the proper threads. Tap the old hole with a larger tap and put a small brass plug in it with Teflon tape to seal it. Jim Patrick

I would try a different petcock.

Humblej wrote: ↑

Fri Oct 25, 2024 9:57 am

I would try a different petcock.

Yes, that. Plus, a bit of JB Weld instead of teflon tape.

Maybe J-B Weld a 1/8" mpt X 1/8" fmpt fitting in the radiator & then you screw the petcock in with tape sealing Teflon.
Craig.

Thanks all for the suggestions.
I think that the radiator has the worn out threads. I'll try some JB weld as soon as I can get it cleaned and dried.
John

Get the area around the hole down to bare metal. Clean up the area around the hole super good with lacquer thinner and rough up the area with 220 sandpaper and wipe down again with lacquer thinner. Spread JB Weld in a radius of 1” around and over the existing hole and make an indentation at the center of the hole with a pencil, where you will drill. After it has started to set up, but is still soft, get a cup of water and with your dampened finger, feather and make the JB Weld glass smooth. Smooth with your dampened finger until satisfied. Let the JB Weld thoroughly cure. Now you can drill and tap a new threaded hole for your petcock with the proper tap.

Or - if you're not a stickler for originality, merely drill & re-tap to 1/4 p. and change out the drain cock.

RajoRacer wrote: ↑

Fri Oct 25, 2024 2:11 pm

Or - if you're not a stickler for originality, merely drill & re-tap to 1/4 p. and change out the drain cock.

Or, use a 1/4 to 1/8 reducer bushing and use the same petcock.

Good point there, Jerry !

It the thread in the radiator outlet is compromised, you could solder/tin the thread on the draincock to compensate. The solder is soft enough to allow the cock to be threaded on, and it will act like a lead gasket at the same time.

Allan from down under.

Thank you all for the ideas. I think I will go with the tinned/soldered petcock route. That makes more sense to me. I will report back when done.
John

Hi all,
Again thanks for the suggestions. I fixed the problem by soldering the petcock. Three times. First time first level of solder wasn't thick enough.
The petcock spun. Second time, layer of solder was too thick The third time worked since I removed some solder. I fitted the petcock and it was tight, but I decided that a little JB Weld was extra insurance.
John

NY John T wrote: ↑

Wed Oct 30, 2024 9:44 am

Hi all,
Again thanks for the suggestions. I fixed the problem by soldering the petcock. Three times. First time first level of solder wasn't thick enough.
The petcock spun.
first layer.jpg
Second time, layer of solder was too thick
second layer.jpg
The third time worked since I removed some solder. I fitted the petcock and it was tight, but I decided that a little JB Weld was extra insurance.
John

Nice work! Thanks for the update!